1. Field of the Invention
The present invention is related to clutches, and more particularly to a bi-directional overrunning clutch for controlling torque transmission to primary drive axles of a working vehicle.
2. Background Art
Simple drive systems for two wheel drive working vehicles, i.e. lawn mowers, lawn vacuums, snow blowers, utility tractors, trimmers, edgers, concrete and asphalt cutters, and the like, typically include a drive shaft or belt connected to a single drive axle, which drives both drive wheels. The principal deficiency with this type of drive system is that the vehicle is inefficient during turning because the wheels rotate on a common shaft, and thus rotate at the same rate of speed.
For instance, when turning such a vehicle, the outer wheel must travel a greater distance than the inner wheel in the same amount of time. However, because the wheels rotate on a common shaft, the result is that differential rotation is not permitted, resulting in one of the wheels slipping or skidding. This slipping/skidding results in premature wear of the wheel, and damage to surfaces on which the vehicle is operating. A lawn mower with this type of drive system can damage the turf under the slipping wheel. Similar inefficiencies are known to four-wheel drive vehicles when traveling on unleveled surfaces, resulting in slipping/skidding of the front or rear axles.
To eliminate the inefficiency in two-wheel drive systems, vehicles are generally provide with a differential between the pair of drive wheels. The differential permits independent or differential rotation of the drive wheels on an axle when the vehicle turns. Differentials, however, have various disadvantages. For example, when one wheel losses traction with the ground, the conventional differential is unable to transmit torque to the opposite wheel. To address this problem, many differentials on the market today use some form of overrunning clutch, or differential lock, to transmit torque when needed to a driven shaft. Co-pending and co-owned U.S. patent application Ser. Nos. 11/090,097 and 11/277,433 describe various bi-directional overrunning clutch designs for controlling torque transmission between two axle shaft segments in a transaxle. Application Ser. Nos. 11/090,097 and 11/277,433 are hereby incorporated in their entirety by reference thereto. What is needed is a bi-directional overrunning clutch suited for transmission of torque between front and rear drive axles in a four-wheel drive system.